1. Field of the Invention
The present invention relates to a recording paper conveyance method, and in particular, to a recording paper conveyance technique used for an ink jet recording apparatus.
2. Description of the Related Art
Conventionally, recording apparatuses such as printers, particularly, ink jet recording apparatuses, use a conveyance mechanism including paper conveyance rollers. More specifically, two rollers, that is, a main roller and a discharge roller, are used to convey a recording paper accurately. A major problem in increasing the accuracy of conveying a recording paper with these rollers involves paper feeding at the transfer point from the main roller to the discharge roller. While the paper feeding at this transfer point is affected by variation in the accuracy of steady feeding operations of the rollers, the paper feeding is also affected by other factors, such as a warp in a roller shaft and an unstable behavior of the rollers when the recording paper is released from the main roller. Generally, it is known that the conveyance accuracy is decreased through the above steady feeding operations.
In response to such decrease in the conveyance accuracy, Japanese Patent Application Laid-Open No. 2008-87341 discusses a recording apparatus. This recording apparatus forms predetermined correction value measurement test patterns and measures conveyance amount errors generated at the transfer point twice. By calculating an average of these measured values, the recording apparatus determines a correction value.
However, when the recording paper is transferred from the main roller to the discharge roller, variation in speed increasing ratio may be caused between the main roller and the discharge roller. When the recording apparatus discussed in Japanese Patent Application Laid-Open No. 2008-87341 calculates the correction value, such variation is also included. The variation in speed increasing ratio between the main roller and the discharge roller are caused to occur by the diameters of the rollers at the macro level and by the eccentricity of the rollers at the micro level. According to Japanese Patent Application Laid-Open No. 2008-87341, it is unclear where the measured conveyance amount errors exist in a variation distribution, and there is no guarantee that the average, that is, the correction value, is the center value of the entire variation distribution. Namely, the correction value is not reliable. Thus, a conveyance amount that does not correspond to the set correction value is generated with a certain probability, resulting in deterioration in image quality.